Gently melt the topping ingredients in small saucepan and set aside to cool.

For the base cream butter and sugar, add vanilla and flour and mix to combine.
Take 3 tablespoons of this mixture, wrap in glapwrap and put in the freezer to harden up a little.
Press the remaining base mixture into the tin. I find it easier to lay gladwrap on top and then press it in especially on a hot day - less sticky this way.

Pour the cooled (not cold) topping mixture over the base.

Retrieve the mixture from the freezer and using a sharp knife cut small lumps of it and randomly drop them onto the topping. You have to work fast otherwise your hands will melt the mixture.
You will end up with a series of little mountains on the top.

Bung it in the oven for approx 30 minutes.
Be sure to check it at 20 and 25 minutes as all oven temperatures vary.
I forgot my oven is hotter and left it the full thirty before checking.
You do want it to become a lovely tan colour though.

Let it cool, cut it up and hide it from your husband and kids!
In saying that it makes a lot and needs to be eaten in a few days otherwise it goes a bit soft.